Materials: How to get this transparent screen look?
This effect could be achieved with 4 nodes. 





Add a emission shader (that your image will plug into)
Add a transparent shader
Add a mix shader 


Plug your two shaders into the mix shader and slide the FAC value to taste. 

After rendering I would bring the image into a compositor and add some glow around the hologram image to make it a little more believable. 

Pics taken from Unsplash.com

Photo by Javier Ramos on Unsplash
Photo by Justin-Lim-500765-unsplash